NSF\/ANSI 58 is the certification standard for point-of-use reverse osmosis systems intended for drinking water. If a supplier tells you their RO system is “NSF certified,” NSF\/ANSI 58 is what they’re referring to \u2014 and what that certification actually covers matters for purchasing decisions, regulatory compliance, and liability.<\/p>\n
The standard has three components:<\/p>\n
The third component is the most important for buyers. NSF certification doesn’t mean an RO system removes everything \u2014 it means the specific claims on that certified product have been tested and verified.<\/p>\n
NSF\/ANSI 58 applies specifically to point-of-use (POU) systems \u2014 countertop, under-sink, or similar units designed for individual use. Industrial and commercial RO systems above a certain size are not subject to NSF\/ANSI 58 certification requirements.<\/p>\n
For commercial applications, the relevant NSF standards are:<\/p>\n
| Contaminant<\/th>\n | Challenge Concentration<\/th>\n | Typical RO Reduction<\/th>\n | Notes<\/th>\n<\/tr>\n<\/thead>\n |
|---|---|---|---|
| Total dissolved solids (TDS)<\/td>\n | 750 mg\/L<\/td>\n | 75\u201398%<\/td>\n | Primary performance metric for most POU systems<\/td>\n<\/tr>\n |
| Lead<\/td>\n | 0.15 mg\/L<\/td>\n | >95%<\/td>\n | Both ionic and particulate lead<\/td>\n<\/tr>\n |
| Nitrate<\/td>\n | 27 mg\/L NO3-N<\/td>\n | 60\u201395%<\/td>\n | Reduction varies significantly by membrane type and recovery<\/td>\n<\/tr>\n |
| Fluoride<\/td>\n | 8 mg\/L<\/td>\n | 90\u201395%<\/td>\n | Tested independently from TDS reduction<\/td>\n<\/tr>\n |
| Arsenic V<\/td>\n | 0.05 mg\/L<\/td>\n | >95%<\/td>\n | Arsenic III requires oxidation pre-treatment for comparable removal<\/td>\n<\/tr>\n |
| Barium<\/td>\n | 10 mg\/L<\/td>\n | >97%<\/td>\n | Often tested alongside radium as a surrogate<\/td>\n<\/tr>\n |
| PFOA \/ PFOS<\/td>\n | 1.5 \u00b5g\/L each<\/td>\n | >96%<\/td>\n | Added to NSF\/ANSI 58 in 2020; validated reductions vary by membrane<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nPFAS and NSF\/ANSI 58: What Changed in 2020<\/h2>\nNSF International added PFOA and PFOS reduction claims to NSF\/ANSI 58 in 2020, creating a certification pathway for manufacturers who want to validate PFAS removal performance. Systems certified for PFOA\/PFOS reduction have been tested to achieve greater than 96% reduction at the challenge concentration.<\/p>\n The standard uses a challenge concentration of 1.5 micrograms per liter (\u00b5g\/L) for both PFOA and PFOS \u2014 substantially higher than the EPA’s 2024 maximum contaminant levels of 4 parts per trillion (0.004 \u00b5g\/L) for PFOA and PFOS individually. Systems that pass the NSF test typically achieve product water PFAS concentrations well below the EPA limits in real-world conditions.<\/p>\n PFAS certification under NSF\/ANSI 58 applies only to the specific compounds tested (PFOA and PFOS as of the original addition). The EPA’s broader PFAS MCLs also cover PFHxS, PFNA, HFPO-DA (GenX), and PFBS\/PFHxS combinations. NSF certification for these additional compounds is being developed.<\/p>\n How to Read an NSF Certification<\/h2>\nNSF certification is product-specific, not company-wide. A manufacturer can have one certified model and twenty uncertified ones. When evaluating a claim:<\/p>\n
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